Mössbauer Effect Studies of Nd₂Fe₁₄₋ₓSiₓB and Y₂Fe₁₄₋ₓSiₓB

The Mössbauer effect spectra of the solid solutions of Nd2Fe14-xSixB with x equal to 0.00, 0.25, 0.50, 0.75, 1.0, 1.5, and 2.0, and Y2Fel4-xSixB with x equal to 0.0, l.0, 1.5, and 2.0 have been measured at 295 K. The results are most consistent with a random distribution of the silicon over the smaller 16k1, 16k2, 8j1, 4c, and 4e iron sites in Nd2Fe14B. Apparently the silicon is, at least in part, excluded from the 8j2 site, the site with the largest Wigner-Seitz volume. The results do not, however, rule out other possible silicon site occupancy models. The isomer shift increases slightly with increasing silicon content, whereas the quadrupole interaction remains virtually constant. The hyperfine fields decrease with increasing silicon content, but the apparent linewidth increases. These changes have been modeled in terms of a distribution of hyperfine fields on each site, a distribution which is determined by a binomial distribution of silicon on the Wigner-Seitz near neighbors of each iron site. The results indicate that silicon in the near neighbor environment of an iron in Nd2Fe12Si2B reduces the transferred hyperfine field at the site by an amount varying from 10 to 20 kOe, depending upon the site